The objectives of this project are: 1) Describe and understand the interactions of bone cells, skin firbroblasts, lymphocytes, and macrophages with the surfaces of bioglasses of varying composition and surface characteristics; and 2) Establish a scientific basis for in vitro evaluation of toxicity and bondability of controlled surface active materials considered for use as implants. Sensitive quantitative assays for alkaline phosphatase and cAMP have been established. The specific activity of alkaline phosphatase in bone cell culture were approximately 10X that in skin fibroblasts. Bone cells in vitro were shown to produce elevated levels of cAMP in response to treatment with either PTH or calcitonin. Growth rates, cell saturation densities, and alkaline phosphatase activities for both bone cells and skin fibroblasts cultured on control substrates compared with bioglasses show no evidence of toxicity. However, the bioglasses develop strong adherence between the cell layer and the active calcium phosphate film forming on the material similar to in vitro bone bonding behavior of these materials. Mechanisms of cell adherence to the bioglasses, evidence for intercellular mineralization in vitro, additional assays for collagen synthesis and macrophage phagocytosis will be studied as a function of composition of the surface active layers on bioglasses. Confirmation that there is no evidence of bioglass toxicity for normal human lymphocytes comparing RNA synthesis of bioglasses and controls will also continue.